Abstract: A gas supply (30) supplies pressurized gas to a nozzle (1) such that a flow of gas is discharged through an aperture (77) defined between a lip (3) of the nozzle and a vibrating diaphragm (9). A liquid dispenser (42) introduces a metered quantity of liquid into the gas flow such that the liquid droplets are atomized by the vibrating diaphragm. The diaphragm is held under tension so that it is vibrated by the gas flow. The supply of gas may be a manually operated displacement or diaphragm pump or may be a pressurized gas container. Metered doses may be dispensed for oral inhalation without providing external energy source for the vibration of the diaphragm.